This invention relates to battery handles for diagnostic medical instruments and apparatus and more particularly to a convertible rechargeable battery handle which can accept both a rechargeable battery pack and standard non-rechargeable cells for providing power to a medical instrument.
In recent years diagnostic medical instruments in general and particularly instruments such as ophthalmoscopes, otoscopes, retinoscopes, transilluminators and the like have been provided with interchangeable and rechargeable battery handles so that the instruments can be used free of any cords or other attachments for supplying the necessary illumination. This has required, of course, that the batteries be periodically recharged and this has been accomplished by various means such as placing the handle in a recharging fixture, disconnecting the instrument head from the handle and plugging the handle into a wall socket and similar means.
These battery handles have proved to be very satisfactory as long as the physician remembers to plug them into a charging fixture when not in use and there is no power failure at the time the battery handle needs recharging. Various systems have been proposed in the past to allow use of standard non-rechargeable cells in a rechargeable battery handle when the battery pack is discharged. In U.S. Pat. No. 4,147,163 an apparatus is shown where the rechargeable cell is longer than the non-rechargeable cells and a spring biased moveable contact is provided to make contact with the charging circuit when a rechargeable battery is installed. The handle can then be inserted in a charging unit to recharge the battery pack. The non-rechargeable cells when installed in the handle, and the contact, are spring biased out of the charging circuit so as to prevent inadvertent charging of the non-rechargeable cells.
U.S. Pat. No. 4,382,219 shows a movable spring biased contact pin in the charging fixture that is adapted to engage a rechargeable battery pack terminal through an aperture in the handle when the handle is positioned in the charger. A stop and flange are provided to prevent the contact pin from making contact with non-rechargeable batteries installed in the handle. In this system the rechargeable battery must have a length equal to or greater than the non-rechargeable cells. Non-rechargeable cells are held in place in the handle by a second spring which acts both as a contact and drive spring.
Neither of the configurations shown would work where the rechargeable battery pack is shorter than the desired nonrechargeable replacement cells. The present invention addresses this problem for those situations where the non-rechargeable cells are longer than the rechargeable battery pack by providing an end cap closure for converting the conventional rechargeable battery handle to a standard non-rechargeable cell battery handle configuration. The present invention has no moving contacts, requires no moving parts, and uses a diode for preventing charging of the non-rechargeable cells. The deflection of the drive spring permits electrical contact through the coaxial spring without movement of any other contacts in a simpler and more economical fashion.